Background: As 61% of new HIV infections in the US occur among men who have sex with men (MSM), effective prevention strategies are needed for this population. Antiretroviral pre-exposure prophylaxis (PrEP) can decrease HIV incidence among MSM and is available for prescribing. However, risk criteria to identify MSM who may benefit from PrEP are unclear given potential harms (toxicities, drug resistance, risk compensation) and the impact of daily medication use on quality of life. Therefore, MSM and healthcare providers are at risk for decisional conflict, the state of uncertainty over the course f action to take, regarding PrEP use. This can lead to decisional regret and poor adherence. There is a need to understand how MSM and providers approach the decision to initiate PrEP and how to optimize this decision making process. Candidate: My career goal is to become an independent investigator with expertise in optimizing clinical decision making for biomedical HIV prevention. Six published or submitted manuscripts (2 first-author) and 6 accepted abstracts (2 first-author oral presentations) focused on PrEP in the last 2 years reflect my commitment to HIV prevention research. To become an independent investigator, I need additional research training, mentorship, and experience. Research: My scientific goal is to understand how MSM and providers approach the decision to initiate PrEP and then develop and evaluate a decision-support intervention to optimize the decision making process. My hypothesis is that shared decision making, a process in which patients and providers weigh risks and benefits of treatments together and then decide on a course of action, can reduce decisional conflict and its adverse consequences. I will test this hypothesis by pursuing 3 specific aims: 1) conduct qualitative interviews to assess how MSM and providers estimate HIV risk and approach trade-offs regarding PrEP use, in order to inform development of a shared decision making Decision Aid; 2) develop a Decision Aid for MSM-provider dyads that decreases MSM decisional conflict regarding PrEP use; and 3) evaluate the impact of the Decision Aid on MSM decisional conflict in clinical settings. Training: The research is supported by courses and/or structured mentoring in qualitative and quantitative methods, decision science, clinical trial design, adherence measures, and issues relevant to research with MSM. Mentorship and Resources: Dr. Ken Mayer, an expert in PrEP and HIV prevention for MSM, is my primary mentor. To achieve my goals, I will leverage his extensive research infrastructure at Fenway Health and the resources of Harvard and Beth Israel Deaconess Medical Center, where I will be appointed as Attending Physician in the Division of Infectious Diseases in July 2012. I will also benefit from a team of dedicated co-mentors in decision science, qualitative research, patient-provider communication, and adherence. The approach is innovative in its application of clinical decision science to HIV prevention. The research is significant because it is expected to fundamentally alter clinical decision making for PrEP and other biomedical prevention strategies.